Flash Communication: Reactions of Borole with Michler’s Ketone Versus Thioketone

In this work, we interrogate the reactivity of pentaphenylborole with 4,4′-bis(dimethylamino)benzophenone (Michler’s ketone) and its heavier congener, bis(dimethylamino)thiobenzophenone (Michler’s thioketone). The ketone inserts the CO unit to generate an unsaturated BOC5 heterocycle while the thioketone coordinates to the boron center but the adduct thermally isomerizes via migration of a C-Ph unit and insertion of the sulfur atom to furnish a BSC3 boracycle with a pendent alkene.